-- Discussion containing changed information from previous version are highlighted. --
059
FXUS66 KMFR 101159
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
459 PDT Fri May 10 2024

...Updated AVIATION discussion...

.DISCUSSION...Our summer like pattern is well underway today.
Skies are clear across the region thanks to east to
northeasterly (offshore) flow brought on by a thermal trough along
the coast. Gusty winds continue this morning along the midslopes
and ridges, though not as strong as Thursday morning. Deep layer
east to northeasterly flow has been in place since Wednesday with
high pressure positioned over the eastern Pacific, low pressure
centered over the Great Basin and a thermal trough along the
coast. This pattern will gradually shift today as the low pressure
to the southeast shifts eastward and the high pressure nudges
over the Pacific Northwest. At the surface, the thermal trough
will move inland. Overall, this will result in weakening offshore
flow today and hot temperatures for inland locations.

The Chetco Effect has been in full swing and temperatures at the
Brookings airport reached 86 degrees yesterday. We do expect another
round of hot temperatures along the coast south of Cape Blanco, but
temperatures should peak fairly early today as the thermal trough
expands and the flow shifts. North of Cape Blanco, however,
temperatures will peak today as the upper ridge takes an east/west
orientation. This pattern tends to result in hot temperatures for
areas north of Cape Blanco and into the Umpqua Basin. Expect upper
70s along the coast north of Cape Blanco with upper 80s, possibly
into the low 90s for Roseburg and surrounding areas. Elsewhere for
inland locations, the strong warming trend will continue into
Saturday for the West Side and into Sunday for the East Side. Expect
high temperatures around 15 degrees above normal, reaching the
warmest values of the year so far.

The pattern takes a more appreciable shift on Sunday as high
pressure aloft gets flattened and weakened by an incoming trough
from the northwest. This will largely be a dry trough, but it will
bring a marine push with cooler onshore flow and a brief cooling
trend through early next week. Models continue to show enough,
though marginal, instability and moisture on Sunday to warrant a
slight chance (15-25%) of thunderstorms for portions of eastern
Siskiyou, Modoc, Lake, and southern portions of Klamath counties.

The upper level ridge rebounds on Monday, rebuilding over the
eastern Pacific and leaving the region in dry and mostly stable
northwest flow Monday into at least midweek. Models do show some
weak instability across southern Siskiyou and Modoc counties on
Monday, but moisture doesn`t look to be sufficient for thunderstorm
development. Temperatures will remain cooler than what is
anticipated this weekend, but still above normal for early-mid May.

Uncertainty increases for the latter half of the week with one model
showing the ridge moving directly overhead leading to a similar
pattern as the one we are currently experiencing and another showing
another mostly dry trough followed by zonal flow. Each model`s
ensembles tend to support the deterministic. A look at the full
suite of ensemble data through the cluster analysis, however, shows
that the majority of solutions favor continued ridging, just with
differences on location and strength of the ridge. Based on this,
expect continued warm temperatures and dry conditions through the
end of the week. /BR-y

&&

.AVIATION...
-- Changed Discussion --
10/12Z TAFs...Clear skies and visibilities will continue
to bring VFR levels across northern California and southern Oregon.
The only possible hazard will be smoke from the Little Yamsay fire
that continues to burn in northeast Klamath County. -TAD
-- End Changed Discussion --

&&

.MARINE...Updated 200 AM Friday, May 10, 2024...Steep seas will
continue in all waters as north winds continue to weaken. Seas will
be calm by later this morning and will remain calm through Saturday
morning.

Steep seas will return as northerly winds increase over outer waters
and a thermal trough starts to develop south of Cape Blanco. These
conditions will build steep seas in waters south of Cape Blanco and
in waters beyond 10 nm from shore north of Cape Blanco. A Small
Craft Advisory will be in place from Saturday at 5 PM through Sunday
at 5 PM to communicate these conditions.

Some amount of hazardous conditions will continue into next week as
the thermal trough strengthens. Current model guidance shows
fluctuating periods of hazardous and gale seas south of Gold Beach
through Wednesday, with steep seas continuing in most other waters.
The exact timing and areas will benefit from further consideration,
but chaotic seas do look likely to continue into the middle of next
week. -TAD

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...CA...None.

PACIFIC COASTAL WATERS...Small Craft Advisory until 5 AM PDT early
     this morning for PZZ350-356-370-376.

&&

$$

MNF/TAD